1. Field of the Invention
The invention relates to a high voltage diode (HV Diode), and more particularly, to a HV diode using conductive drift rings for providing stable breakdown voltage.
2. Description of the Prior Art
Double diffuse drain (DDD) is a diode structure that is applied to HVMOS transistors. The high-voltage diode structure is able to provide the HVMOS transistor with a higher breakdown voltage. This can prevent a high voltage, such as electrostatic discharge (ESD), from damaging the transistor. Furthermore, the hot electron effect resulting from short channel is avoided.
Conventional HV diode typically includes a substrate, a n+ doping region disposed in the substrate and a field oxide layer surrounding the n+ doping region. However, the conventional HV diode framework has some drawbacks. For instance, a breakdown is often found at the junction between the n+ doping region and the field oxide layer after long period of operation to cause a serious shift to the breakdown voltage of the device. Hence, how to provide a stable and reliable structure for resolving this issue has become and important task in this field.